Guides to Time Math and Telling Time
Plain explanations of the time math behind the calculators, with worked examples.
All guides
- How to add and subtract timeCarrying and borrowing at 60, clock times, midnight, and negative results.
- Is 12 AM midnight or noon? 12 AM vs 12 PM explainedThe convention, which day midnight belongs to, and how to write deadlines clearly.
- Elapsed time worksheets: word problems with answersPrintable practice from same-hour to across midnight, with worked answers.
- How to add and subtract time in ExcelTotals over 24 hours, overnight spans, decimal hours, and negative times.
- What is Tabata? The 20/10 format and how to time itWhat the original study tested, how gyms use the name now, and a round-by-round schedule.
These guides are written by Cedrick Reese for Timer Calculator. Each one explains the math or timing behind one of the site's tools, cites its outside sources on the page, and its worked examples were run through the matching calculator or timer, so the guide and the tool give the same answer.